Facebook just made several changes to its self-serve ad options. The big one: That advertisers can now buy mobile-only news feed Sponsored Stories — potentially huge for app developers looking to buy installs.

This could be a key step for Facebook to monetize its massive mobile audience in a significant way — a constant topic among skeptics in the run-up to the company’s IPO. Facebook was already moving into mobile advertising, but this new option should be especially attractive to advertisers who want to reach a mobile-only audience.

For example, this could be a big opportunity for smartphone app developers, who can now target potential users when they’re actually on their phones, offering them a link that goes directly to the download page in the app store. This could also be tempting to local businesses (especially when coupled with Facebook’s zip code-level ad targeting) who want to reach users when they’re out-and-about on their phones.

Here’s the full list of placements that Facebook says advertisers can now buy through its API and Power Editor: